Method of forming micropatterns utilizing silylation and overall energy beam exposure

ABSTRACT

A resist film is formed on a semiconductor substrate by using a chemical amplification resist which generates an acid in response to the radiation of KrF excimer laser light and which reacts with the acid. If the resist film is irradiated with the KrF excimer laser light through a mask, the acid is generated in the surface of an exposed portion of the resist film, so that the surface of the exposed portion is made hydrophilic by the acid. If water vapor is supplied to the surface of the resist film, water is diffused from the surface of the exposed portion into a deep portion. If vapor of methyltriethoxysilane is sprayed onto the surface of the resist film in air at a relative humidity of 95%, an oxide film with a sufficiently large thickness is selectively formed on the surface of the exposed portion.

This is divisional of application Ser. No. 08/497,471, filed Jun. 30,1995, now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates to a method of forming micropatterns inthe process of fabricating semiconductor integrated-circuit devices orthe like.

In a conventional process of manufacturing ICs or LSIs, patterns aregenerally formed by photolithography using an ultraviolet ray. With theminiaturization of semiconductor devices, however, a light source of ashorter wavelength has been used increasingly. As a resist compatiblewith the light source of a shorter wavelength, there has been used achemical amplification resist which provides high sensitivity as well ashigh resolution (e.g. O. NALAMASU et. al. Proc. SPIE, 1282., 32(1990)).

The chemical amplification resist is a multi-component resist containingan acid generator which generates an acid in response to the radiationof an energy beam and a compound which reacts with the acid. Amongpolymers which react with an acid, a compound with the structure asshown in the following Formula 1! is known. ##STR1## where R is analkoxycarbonyl, alkyl, alkoxyalkyl, alkylsilyl, tetrahydropyranyl,alkoxycarbonylmethyl, or like group, which is easily decomposed by anacid. Such a chemical amplification resist contains, as its maincomponent, a polymer which presents a low absorption index with respectto light in the range of shorter wavelengths, such as a derivative ofpolyvinyl phenol. Accordingly, the transparency of the chemicalamplification resist is increased and the reaction of the resistproceeds through a chain reaction induced by an acid catalyst, resultingin high sensitivity and high resolution. Hence, the chemicalamplification resist is considered as a promising material for formingmicropatterns by utilizing a light source of a shorter wavelength.

At present, a vigorous study is being directed to the formation of aresist pattern of 0.2 μm or less in size in accordance with adeep-ultraviolet-ray exposure method using such a chemical amplificationresist. However, since the aspect ratio of a resist pattern becomeshigher with the increasing miniaturization thereof, a conventional wetdeveloping method is disadvantageous for the following reason.Specifically, a resist film coated on a semiconductor substrate isexposed to a deep ultraviolet ray and then developed, resulting in aresist pattern. After that, a developing solution and the resistmaterial dissolved in the developing solution are washed away from theresist pattern with pure water. Finally, the resist pattern is subjectedto spin drying, which involves the rotation of the resist pattern at ahigh speed.

In the step of drying the resist pattern, however, large surface tensionacts on pure water 82 remaining between adjacent resist patterns 81formed on that region of a semiconductor substrate 80 having a highaspect ratio, as shown in FIG. 16(a). As a result, the resist patterns81 are distorted or broken by the large surface tension exerted thereon,thereby causing a phenomenon that the resist patterns are leaningagainst their adjacent resist patterns, as shown in FIGS. 16(b) and16(c). The phenomenon is similarly observed in the case of using anormal resist, instead of using the chemical amplification resist.

To eliminate the disadvantage, there has been proposed a method forforming a resist pattern by performing dry etching with respect to aresist film of chemical amplification type, as disclosed in U.S. Pat.No. 5,278,029. Below, a description will be given to the method withreference to FIGS. 17(a) and 17(b) and to FIGS. 18(a) and 18(b).

Initially, as shown in FIG. 17(a), a resist film 91 of chemicalamplification type coated on a semiconductor substrate 90 is irradiatedwith KrF excimer laser light 93 through a mask 92, thereby generating anacid in an exposed portion 91a of the resist film 91. The exposedportion 91a is made hydrophilic by the action of the resulting acid andhence is apt to absorb water in the atmosphere. Consequently, a thinabsorption layer 94 of water is naturally formed on the surface of theexposed portion 91a.

Subsequently, an alkoxysilane gas is introduced into the surface of theresist film 91, thereby forming an oxide film 95 on the surface of theexposed portion 91a, as shown in FIG. 18(a). Thereafter, dry etching byRIE using an O₂ plasma 96 is performed with respect to the resist film91 through the oxide film 95 as a mask, thereby forming a minusculeresist pattern 97, as shown in FIG. 18(b).

However, the resist pattern actually formed in accordance with the abovemethod was disadvantageous in that the oxide film 95 was caused to flowin a step of evaporating an alcohol, resulting in an increased degree ofedge roughness of the oxide film 95, which deteriorates the sizeprecision of the resist pattern. As a result of diagnostic examination,the deformation of the oxide film 95 was attributed to the thinness ofthe oxide film 95.

SUMMARY OF THE INVENTION

In view of the foregoing, an object of the present invention is toenable the formation of a thick oxide film in an exposed portion of aresist film by supplying a metal alkoxide to the surface of the resistfilm, thereby increasing the size precision of a resist pattern.

To attain the above object, the present inventors examined the reasonwhy only a thin oxide film is formed when an alkoxysilane gas issupplied to the surface of the exposed portion and found the followingfact. That is, since a relative humidity in the environment inside aclean room is kept as low as 50% or less, the water in the atmosphere isdifficult to be diffused into the resist film, so that it is diffusedonly in the surface region of the resist film. Hence, if the exposedportion of the resist film is simply allowed to stand in the atmosphere,the thickness of the oxide film formed on the surface of the exposedportion of the resist film becomes small. The present invention, whichhas been achieved based on the above finding, is for forming a metaloxide film with a sufficiently large thickness by causing the exposedportion of the resist film to absorb water and then supplying water anda metal alkoxide thereto.

A first method of forming a micropattern according to the presentinvention comprises: a first step of forming a resist film by applying,onto a semiconductor substrate, a resist containing an acid generatorwhich generates an acid in response to the radiation of an energy beam;a second step of causing the acid generator contained in an exposedportion of the resist film to generate the acid by irradiating theresist film with the energy beam; a third step of causing the exposedportion of the resist film, in which the acid has been generated, toabsorb water: a fourth step of forming a metal oxide film in the exposedportion of the resist film by supplying water and a metal alkoxide to asurface of the exposed portion of the resist film having absorbed thewater: and a fifth step of forming a resist pattern by performing dryetching with respect to the above resist film by using the metal oxidefilm as a mask.

According to the first method of forming a micropattern, since water isabsorbed into the exposed portion of the resist film in which the acidhas been generated, the water is diffused from the surface thereof intoa deep portion. Moreover, since the metal oxide film is formed in theexposed portion of the resist film by supplying the water and metalalkoxide to the surface of the exposed portion of the resist film havingabsorbed water, the growth of the metal oxide film proceeds toward theinterior of the resist film. Therefore, the water absorbed by the resistfilm is, prevented from being evaporated, while water required to formthe metal oxide film is supplied, so that water sustains its state ofequilibrium, thereby forming a metal oxide film with a sufficientlylarge thickness to withstand dry etching. Consequently, a resist patternwith a high aspect ratio can be formed with high precision.

In the fourth step, either vapor of the metal alkoxide or a solution ofthe metal alkoxide may be supplied.

Preferably, the first method of forming a micropattern furthercomprises, between the first step and the second step, a step offorming, in a surface of the resist film, a resin film made of acontrast enhanced resin which shows, in response to the radiation of theenergy beam, an increased transmittance with respect to the energy beam,and, between the second step and the third step, a step of removing theresin film formed on the surface of the resist film.

Since this arrangement enhances the contrast of light intensity on theresist film, the acid is efficiently generated in the exposed portion.As a result, the hydrophilicity of the exposed portion is increased andwater is efficiently absorbed. Consequently, the metal oxide film growstoward the interior of the resist, thereby successfully forming a metaloxide film with a sufficiently large thickness.

In the first method of forming a micropattern, the fourth steppreferably comprises a step of forming a metal oxide film in the exposedportion of the resist film by alternately performing the step ofsupplying water and the metal alkoxide to the surface of the exposedportion of the resist film having absorbed the water and a step ofsupplying a dry inert gas to the surface of the exposed portion of theresist film having absorbed the water.

With the arrangement, an alcohol generated by the supply of the metalalkoxide and imparting mobility to the metal oxide film is evaporatedeach time it is generated, so that the mobility of the metal oxide filmis surely lowered. Consequently, the metal oxide film excellentlyretains its initial configuration, thereby forming a resist pattern witha high aspect ratio with extremely high precision.

Preferably, the first method of forming a micropattern furthercomprises, between the fourth step and the fifth step, a step of curingthe metal oxide film formed in the fourth step. With the arrangement,the mobility of the metal oxide film is surely lowered and the metaloxide film excellently retains its initial configuration. Consequently,a resist pattern with a high aspect ratio can be formed with extremelyhigh precision.

In the first method of forming a micropattern, a thickness of the metaloxide film formed in the fourth step is preferably 100 nm or more. Withthe arrangement, the metal oxide film excellently retains its initialconfiguration, so that a resist pattern with a high aspect ratio can beformed with extremely high precision.

In the first method of forming a micropattern, the acid generated fromthe acid generator in the second step is preferably a sulfonic acid.

A second method of forming a micropattern according to the presentinvention comprises: a first step of forming a resist film by applying,onto a semiconductor substrate, a resist containing a base generatorwhich generates a base in response to the radiation of an energy beam: asecond step of causing the base generator contained in an exposedportion of the resist film to generate the base by irradiating theresist film with the energy beam; a third step of causing the exposedportion of the resist film, in which the base has been generated, toabsorb water; a fourth step of forming a metal oxide film in the exposedportion of the resist film by supplying water and a metal alkoxide to asurface of the exposed portion of the resist film having absorbed thewater: and a fifth step of forming a resist pattern by performing dryetching with respect to the resist film by using the metal oxide film asa mask.

According to the second method of forming a micropattern, a metal oxidefilm with a sufficiently large thickness to withstand dry etching can beformed, similarly to the first method of forming a micropattern, therebyforming a resist pattern with a high aspect ratio with high precision.

In the fourth step of the second method of forming a micropattern,either vapor of the metal alkoxide or a solution of the metal alkoxidemay be supplied.

Preferably, the second method of forming a micropattern furthercomprises, between the first step and the second step, a step offorming, in a surface of the resist film, a resin film made of acontrast enhanced resin which shows, in response to the radiation of theenergy beam, an increased transmittance with respect to the energy beam,and, between the second step and the third step, a step of removing theresin film formed on the surface of the resist film. With thearrangement, the contrast of light intensity on the resist film isenhanced, so that the base is efficiently generated in the exposedportion, resulting in increased hydrophilicity of the exposed portion.Consequently, a metal oxide film with a sufficiently large thickness canbe formed excellently.

In the second method of forming a micropattern, the fourth steppreferably comprises a step of forming a metal oxide film in the exposedportion of the resist film by alternately performing the step ofsupplying water and the metal alkoxide to the surface of the exposedportion of the resist film having absorbed the water and a step ofsupplying a dry inert gas to the surface of the exposed portion of theresist film having absorbed the water. With the arrangement, an alcoholgenerated by the supply of the metal alkoxide and imparting mobility tothe metal oxide film is evaporated each time it is generated, so thatthe mobility of the metal oxide film is surely reduced. Consequently,the metal oxide film excellently retains its initial configuration,thereby forming a resist pattern with a high aspect ratio with extremelyhigh precision.

Preferably, the second method of forming a micropattern furthercomprises, between the fourth step and the fifth step, a step of curingthe metal oxide film formed in the fourth step. With the arrangement,the mobility of the metal oxide film is surely lowered and the metaloxide film excellently retains its initial configuration. Consequently,a resist pattern with a high aspect ratio can be formed with extremelyhigh precision.

In the second method of forming a micropattern, a thickness of the metaloxide film formed in the fourth step is preferably 100 nm or more. Withthe arrangement, the metal oxide film excellently retains its initialconfiguration, so that a resist pattern with a high aspect ratio can beformed with extremely high precision.

In the second method of forming a micropattern, the base generated fromthe base generator in the second step is preferably an amine.

A third method of forming a micropattern according to the presentinvention comprises: a first step of forming a resist film by applying,onto a semiconductor substrate, a resist containing a compound which iscrosslinked in response to the radiation of an energy beam; a secondstep of crosslinking an exposed portion of the resist film byirradiating the resist film with the energy beam; a third step offorming a silylated layer in an unexposed portion of the resist film bysupplying a silylating agent to a surface of the resist film; a fourthstep of irradiating the silylated layer with a high energy beam; and afifth step of forming a resist pattern by performing etching withrespect to the resist film by using, as a mask, the silylated layerwhich has been irradiated with the high energy beam.

According to the third method of forming a micropattern, the irradiationof the silylated layer formed in the unexposed portion of the resistfilm with the high energy beam causes the oxidative decomposition andvolatilization of a carbon compound composing the silylated layer,resulting in an increased concentration of silicon in the silylatedlayer and an increased selectivity to the silylated layer and the resistfilm. Consequently, a resist pattern with a high aspect ratio can beformed with high precision.

A fourth method of forming a micropattern according to the presentinvention comprises: a first step of applying, onto a semiconductorsubstrate, a resist film; a second step of exposing the resist film suchthat a pattern is transferred thereto; a third step of forming a resistpattern by developing the exposed resist film with a developingsolution; and a fourth step of washing away the developing solution anda resist material dissolved in the developing solution with a rinsecontaining a surface-active agent.

According to the fourth method of forming a micropattern, the developingsolution and the resist material dissolved in the developing solutionare washed away with a rinse containing a surface-active agent.Accordingly, the surface tension acting on the rinse between minusculeresist patterns is reduced, so that the resist patterns are no moreleaning against each other. Consequently, a resist pattern with a highaspect ratio can surely be formed.

In the fourth method of forming a micropattern, the surface-active agentcontained in the rinse in the fourth step is preferably polyoxyethylenepropylene glycol.

In the fourth method of forming a micropattern, the resist film in thefirst step is preferably composed of a chemical amplification resistcontaining an acid generator which generates an acid in response to theradiation of an energy beam and a compound in which at least a part of aphenolic hydroxy group is substituted by a protecting group eliminatedby the acid. In this case, it is preferred that the fourth method offorming a micropattern further comprises, between the second step andthe third step, a step of heating the exposed resist film. With thearrangement, the action of the acid to eliminate the protecting group isactivated by the application of heat, so that the reaction of developingthe resist film is accelerated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(a) to 1(c) and FIGS. 2(a) and 2(b) are cross sections showingindividual steps of a method of forming a micropattern according to afirst embodiment of the present invention;

FIG. 3(a) is a perspective cross section of a metal oxide film formed inaccordance with the method of forming a micropattern according to theabove first embodiment and FIG. 3(b) is a cross section of a resistpattern formed in accordance with the method of forming a micropatternaccording to the above first embodiment;

FIGS. 4(a) to 4(c) and FIGS. 5(a) and 5(b) are cross sections showingindividual steps of a method of forming a micropattern according to asecond embodiment of the present invention;

FIGS. 6(a) and 6(b) and FIGS. 7(a) and 7(b) are cross sections showingindividual steps of a method of forming a micropattern according to athird embodiment of the present invention;

FIGS. 8(a) to 8(c) and FIGS. 9(a) to 9(c) are cross sections showingindividual steps of a method of forming a micropattern according to afourth embodiment of the present invention;

FIGS. 10(a) to 10(c), FIGS. 11(a) and 11(b), and FIGS. 12(a) and 12(b)are cross sections showing individual steps of forming a micropatternaccording to a fifth embodiment of the present invention;

FIGS. 13(a) to 13(c) and FIGS. 14(a) and 14(b) are cross sectionsshowing individual steps of a method of forming a micropattern accordingto a sixth embodiment of the present invention;

FIG. 15(a) is a perspective cross section of a resist pattern formed inaccordance with a conventional method of forming a micropattern and FIG.15(b) is a perspective cross section of a resist pattern formed inaccordance with a method of forming a micropattern according to aseventh embodiment of the present invention;

FIGS. 16(a) to 16(c) are cross sections for illustrating a disadvantageof a first conventional method of forming a micropattern;

FIGS. 17(a) and 17(b) and FIGS. 18(a) and 18(b) are cross sectionsshowing individual steps of a second conventional method of forming amicropattern; and

FIG. 19 is a perspective cross section for illustrating a disadvantageof the second conventional method of forming a micropattern.

DETAILED DESCRIPTION OF THE INVENTION (First Embodiment)

FIGS. 1(a) to 1(c) and FIGS. 2(a) and 2(c) are cross sections showingindividual steps of a method of forming a micropattern according to afirst embodiment of the present invention.

As a chemical amplification resist there is used a resist containing anacid generator which generates an acid in response to the radiation ofan energy beam, such as a copolymer of1,2,3,4-tetrahydronaphthyridineimino p-styrenesulfonate (NISS) as theacid generator and methyl methacrylate (MMA).

Initially as shown in FIG. 1(a), the above chemical amplification resistis applied onto a semiconductor substrate 10 made of silicon by spincoating and then heated for 60 seconds at a temperature of 90° C.,thereby forming a resist film 11 with a thickness of 1.2 μm. Theresulting resist film 11 is then irradiated with KrF excimer laser light13 as the energy beam through a mask 12, thereby transferring thepattern of the mask 12 to the resist film 11 by exposure. As a result,NISS is decomposed in the surface of an exposed portion 11a of theresist film 11 to generate an acid, which renders the surface of theexposed portion 11a of the resist film 11 hydrophilic.

Next, as shown in FIG. 1(b), the semiconductor substrate 10 is kept inair at a temperature of 30° C. and a relative humidity of 95% for 30minutes, thereby supplying water vapor 14 to the surface of the resistfilm 11. As a result, the surface of the exposed area 11a of the resistfilm 11 absorbs the water vapor 14, so that water is diffused from thesurface of the exposed portion 11a of the resist film 11 into a deepportion, e.g. a portion 100 nm deep.

Next, as shown in FIG. 1(c), vapor 15 of methyltriethoxysilane (MTEOS)as an metal alkoxide is sprayed onto the surface of the resist film 11for 3 minutes, while the semiconductor substrate 10 is kept in the airat a temperature of 30° C. and a relative humidity of 95%, therebyselectively forming an oxide film 16 on the surface of the exposedportion 11a of the resist film 11. In this case, the acid (H⁺) resultingfrom the decomposition of NISS serves as a catalyst and induces areaction as represented by Formula 2!, thereby forming the oxide film 16and generating an alcohol.

Since the water vapor 14 is supplied to the resist film 11 so that thewater is diffused from the surface of the exposed portion 11a of theresist film 11 into a deep portion in the step shown in FIG. 1(b), thegrowth of the oxide film 16 proceeds toward the interior of the resistfilm 11, so that the oxide film 16 with a sufficiently large thicknesscan be formed. Moreover, since MTEOS is supplied to the resist film 11in the air at a relative humidity of 95% in the step shown in FIG. 1(c),the evaporation of the water absorbed by the resist film 11 isprevented, while the water required to form the oxide film 16 issupplied, so that water sustains its state of equilibrium. Consequently,the oxide film 16 with a sufficiently large thickness to withstand RIE(reactive ion etching) using an O₂ plasma, which will be describedlater, can be formed. ##STR2##

Next, the resist film 11 is heated for 60 seconds at a temperature of90° C. to volatilize the generated alcohol and unreacted water, as shownin FIG. 2(a), thereby curing the oxide film 16. As shown in FIG. 3(a),the oxide film 16 thus obtained retains its initial configuration.

Table 1! shows the relationship between the period during which watervapor is supplied and the edge roughness of the resulting resistpattern. From Table 1!, it can be appreciated that, if the depth reachedby diffused water is 100 nm or more, the resist pattern presents areduced degree of edge roughness. Thus, the size precision of the resistpattern can be increased by regulating the depth reached by diffusedwater.

                  TABLE 1                                                         ______________________________________                                        WATER VAPOR  0 min    10 min   20 min 30 min                                  SUPPLY PERIOD                                                                 DEPTH REACHED BY                                                                           approx.  50 nm    100 nm 200 nm                                  DIFFUSED WATER                                                                             0 nm                                                             EDGE ROUGHNESS                                                                             x        x        ∘                                                                        ∘                           OF PATTERN                                                                    ______________________________________                                    

Next, as shown in FIG. 2(b), RIE is conducted using an O₂ plasma 17through the cured oxide film 16 serving as a mask, thereby forming aresist pattern 18. In this case, the RIE using an O₂ plasma is conductedby means of a parallel plate RIE apparatus under the conditions ofpower: 900 W, pressure: 0.7 Pa, and flow rate: 40 SCCM.

FIG. 3(b) shows the configuration of the resist pattern 18 with 0.2-μmlines and spaces formed in accordance with the method of forming amicropattern described above, in which exposure by means of a KrFexcimer laser stepper having a numerical aperture of 0.42 is conductedusing an alternating phase shifting mask. In this case, the thickness ofthe resist film 11 is 1.2 μm, so that the resist pattern 18 with a highaspect ratio of 6 or more can be formed.

Thus, according to the first embodiment, the oxide film 16 isselectively formed on the surface of the resist film 11 and the RIEusing an O₂ plasma is performed with respect to the resist film 11through the oxide film 16 as a mask, thereby conducting dry development.As a result, the problem of pattern collapse due to wet development iseliminated, while the oxide film 16 can retain its initial configurationexcellently. Consequently, a micropattern with a high aspect ratio canbe formed with high precision. Moreover, in the step of diffusing waterin the exposed portion 11a of the resist film 11, the depth reached bydiffused water can be controlled by regulating the period during whichthe water vapor 14 is supplied, i.e., the period during which thesemiconductor substrate 10 is kept in the air at a temperature of 30° C.and a relative humidity of 95%.

Although the first embodiment uses a copolymer of NISS and MMA as achemical amplification resist, it is also possible to use polyvinylphenol, a novolac resin, or the like as a compound which reacts with theacid, instead of MMA. As an acid generator, a generator of a sulfonicacid or the like may be used instead of NISS.

Although MTEOS is used as vapor of an metal alkoxide, it is alsopossible to alternatively use another metal alkoxide such astetramethylorthosilicate or tetraethylorthosilicate.

Although the RIE using an O₂ plasma is used as a method of drydevelopment, ECR (electron cyclotron resonance etching) using an O₂plasma or the like may be used instead.

Although the KrF excimer laser light is used as a light source forexposure, ArF excimer laser light or an X-ray may be used instead.

Although the semiconductor substrate 10 is kept in the water vapor inthe step of diffusing water in the surface of the exposed portion 11a ofthe resist film 11, it is also possible to alternatively supply liquidwater to the resist film 11 overlying the semiconductor substrate 10.However, the supply of water in vapor phase is more preferable than thesupply of water in liquid phase, since the diffusion of water in vaporphase proceeds more swiftly, resulting in an increased thickness of theoxide film 16.

(Second Embodiment)

FIGS. 4(a) to 4(c) and FIGS. 5(a) and 5(b) are cross sections showingindividual steps of a method of forming a micropattern according to asecond embodiment of the present invention.

As a chemical amplification resist, there is used a resist containing abase generator which generates a base in response to the radiation of anenergy beam, such as a mixture of 2-nitrobenzyl carbamate as a basegenerator and poly(methyl methacrylate) (PMMA).

Initially, as shown in FIG. 4(a), a resist composed of the abovechemical amplification resist is applied onto a semiconductor substrate20 made of silicon by spin coating and then heated for 60 seconds at atemperature of 90° C., thereby forming a resist film 21 with a thicknessof 1.2 μm. The resulting resist film 21 is then irradiated with KrFexcimer laser light 23 as an energy beam through a mask 22, therebytransferring the pattern of the mask 22 to the resist film 21 byexposure. As a result, 2-nitrobenzyl carbamate is decomposed in thesurface of an exposed portion 21a of the resist film 21 to generate anamine (base), which renders the surface of the exposed portion 21a ofthe resist film 21 hydrophilic.

Next, as shown in FIG. 4(b), the semiconductor substrate 20 is kept inair at a temperature of 30° C. and a relative humidity of 95% for 30minutes, thereby supplying water vapor 24 to the surface of the resistfilm 21. As a result, water is diffused from the surface of the exposedportion 21a of the resist film 21 into a deep portion. e.g., a portion100 nm deep.

Next, vapor 25 of MTEOS is sprayed onto the surface of the resist film21 for, e.g., 3 minutes, while the semiconductor substrate 20 is kept inthe air at a temperature of 30° C. and a relative humidity of 95%,thereby selectively forming an oxide film 26 on the surface of theexposed portion 21a of the resist film 21. In this case, the amine(R--NH₃ ⁺) resulting from the decomposition of 2-nitrobenzyl carbamateserves as a catalyst and induces a reaction as represented by Formula3!, thereby forming the oxide film 26 and generating an alcohol.##STR3##

Next, the resist film 21 is heated for 60 seconds at a temperature of90° C. to volatilize the generated alcohol and unreacted water, as shownin FIG. 5(a), thereby curing the oxide film 26. The oxide film 26 thusobtained retains its initial configuration.

Next, as shown in FIG. 5(b), RIE is conducted using an O₂ plasma 27through the cured oxide film 26 serving as a mask, thereby forming aresist pattern 28. In this case, the RIE using an O₂ plasma is conductedby means of a parallel plate RIE apparatus under the conditions ofpower: 900 W, pressure: 0.7 Pa, and flow rate: 40 SCCM.

Thus, according to the second embodiment, the oxide film 26 isselectively formed on the surface of the resist film 21 and the RIEusing an O₂ plasma is performed with respect to the resist film 21through the oxide film 26 as a mask, thereby conducting dry development.As a result, the problem of pattern collapse due to wet development iseliminated, while the oxide film excellently retains its initialconfiguration. Consequently, a micropattern with a high aspect ratio canbe formed with high precision. Moreover, in the step of diffusing waterin the exposed portion 21a of the resist film 21, the depth reached bydiffused water can be controlled by regulating the period during whichthe water vapor 24 is supplied, i.e., the period during which thesemiconductor substrate 20 is kept in the air at a temperature of 30° C.and a relative humidity of 95%. Similarly to the first embodiment, wateris preferably diffused from the surface of the resist film 21 to a depthof 100 nm or more, since this prevents the oxide film 26 from flowing.

Although the second embodiment uses PMMA as a compound which composesthe chemical amplification resist and which reacts with the base,polyvinyl phenol or a novolac resin may be used instead. Although2-nitrobenzyl carbamate is used as a base generator, it is not limitedthereto.

Although MTEOS is used as a metal alkoxide, it is also possible toalternatively use another metal alkoxide such astetramethylorthosilicate or tetraethylorthosilicate.

Although the RIE using an O₂ plasma is used as a method of drydevelopment, ECR (electron cyclotron resonance etching) using an O₂plasma or the like may be used instead.

Although the KrF excimer laser light is used a light source forexposure, ArF excimer laser light or an X-ray may be used instead.

Although the semiconductor substrate 20 is kept in the water vapor inthe step of diffusing water in the surface of the exposed portion 21a ofthe resist film 21, it is also possible to alternatively supply liquidwater to the resist film 21 overlying the semiconductor substrate 20.

(Third Embodiment)

FIGS. 6(a) to 6(c) and FIGS. 7(a) and 7(b) are cross sections showingindividual steps of a method of forming a micropattern according to athird embodiment of the present invention. As a chemical amplificationresist, the third embodiment uses a copolymer of NISS and MMA.

Initially, as shown in FIG. 6(a), a resist composed of the abovechemical amplification resist is applied onto a semiconductor substrate30 made of silicon by spin coating and then heated for 60 seconds at atemperature of 90° C., thereby forming a resist film 31 with a thicknessof 1.2 μm. The resulting resist film 31 is then irradiated with KrFexcimer laser light 33 as an energy beam through a mask 32, therebytransferring the pattern of the mask 32 to the resist film 31 byexposure. As a result, NISS is decomposed in the surface of an exposedportion 31a of the resist film 31 to generate an acid, which renders thesurface of the exposed portion 31a of the resist film 31 hydrophilic.

Next, as shown in FIG. 6(b), water 34 is kept on the surface of theresist film 31 for 30 minutes. As a result, the water is diffused fromthe surface of the exposed portion 31a of the resist film 31 into a deepportion, e.g., a portion 100 nm deep.

Subsequently, the surface of the resist film 31 is subjected to spindrying and then an alkoxysilane solution 35 as a metal alkoxide is kepton the resist film 31 for 5 minutes, thereby selectively forming anoxide film 36 on the surface of the exposed portion 31a of the resistfilm 31. The alkoxysilane solution used in the present embodiment isobtained by mixing MTEOS at a concentration of 0.2 mol/l into a mixtureof hexane and acetone. The mixture ratio of hexane to acetone is 9:1.Thereafter, the resist film 31 and the oxide film 36 is rinsed withhexane, followed by spin drying. In this case, an acid resulting fromthe decomposition of NISS serves as a catalyst and induces a reaction asrepresented by the above formula 2!, thereby forming the oxide film 86and generating an alcohol.

Next, as shown in FIG. 7(b), RIE is conducted using an O₂ plasma 37through the cured oxide film 36 serving as a mask, thereby forming aresist pattern 38. In this case, the RIE using an O₂ plasma is conductedby means of a parallel plate RIE apparatus under the conditions ofpower: 900 W, pressure: 0.7 Pa, and flow rate: 40 SCCM.

Thus, according to the third embodiment, the oxide film 36 isselectively formed on the surface of the resist film 31 and the RIEusing an O₂ plasma is performed with respect to the resist film 31through the oxide film 36 as a mask, thereby conducting dry development.As a result, the problem of pattern collapse due to wet development iseliminated, while the oxide film excellently retains its initialconfiguration. Consequently, a micropattern with a high aspect ratio canbe formed with high precision. Moreover, in the step of diffusing waterin the exposed portion 31a of the resist film 31, the depth reached bydiffused water can be controlled by regulating the period during whichthe water 34 is kept on the surface of the resist film 31. Similarly tothe first embodiment, water is preferably diffused from the surface ofthe resist film 31 to a depth of 100 nm or more, since this prevents theoxide film 36 from flowing.

Although the third embodiment uses a copolymer of NISS and MMA as achemical amplification resist, it is also possible to use polyvinylphenol, a novolac resin, or the like as a compound which reacts with theacid, instead of MMA. As an acid generator, a generator of a sulfonicacid or the like may be used instead of NISS.

Although MTEOS is used as a metal alkoxide, it is also possible toalternatively use another metal alkoxide such astetramethylorthosilicate or tetraethylorthosilicate.

Although the RIE using an O₂ plasma is used as a method of drydevelopment, ECR using an O₂ plasma or the like may be used instead.

Although the KrF excimer laser light is used as the light source forexposure, ArF excimer laser light or an X-ray may be used instead.

Although water is kept on the surface of the resist film 31 in the stepof diffusing water in the surface of the exposed portion 31a of theresist film 31, it is also possible to alternatively keep thesemiconductor substrate 30 in water vapor.

(Fourth Embodiment)

FIGS. 8(a) to 8(c) and FIGS. 9(a) to 9(c) are cross sections showingindividual steps of a method of forming a micropattern according to afourth embodiment of the present invention. As a chemical amplificationresist, the fourth embodiment uses a copolymer of NISS and MMA.

Initially, as shown in FIG. 8(a), a resist composed of the abovechemical amplification resist is applied onto a semiconductor substrate40 made of silicon by spin coating and then heated for 60 seconds at atemperature of 90° C., thereby forming a resist film 41 with a thicknessof 1.2 μm. Onto the resulting resist film 41 is then applied a contrastenhanced resin containing 5-diazo-meldrum's acid by spin coating andthen heated for 60 seconds at a temperature of 90° C., thereby forming aresin film 42 with a thickness of 0.1 μm.

Next, as shown in FIG. 8(b), the resist 41 is then irradiated with KrFexcimer laser 44 as an energy beam through a mask 43, therebytransferring the pattern of the mask 43 to the resist film 41. As aresult, NISS is decomposed in the surface of an exposed portion 41a ofthe resist film 41 to generate an acid, which renders the surface of theexposed portion 41a of the resist film 41 hydrophilic. In this case,5-diazo-meldrum's acid contained in the resin film 42 is decomposed bythe KrF excimer laser light 44, thereby increasing the transmittancewith respect to the KrF excimer laser light 44. Consequently, thecontrast of light intensity on the surface of the resist film 41 isenhanced, so that the acid is efficiently generated in the exposedportion 41a. The generation of the acid renders the surface of theexposed portion 41a of the resist film 41 hydrophilic.

Next, as shown in FIG. 8(c), after removing the resin film 42, thesemiconductor substrate 40 is kept in air at a temperature of 30° C. anda relative humidity of 95% for a specified period of time, therebysupplying water vapor 45 to the surface of the resist film 41. As aresult, the surface of the exposed area 41a of the resist film 41absorbs the water vapor 45, so that water is diffused from the surfaceof the exposed portion 41a of the resist film 41 into a deep portion,e.g., a portion 100 nm deep.

Next, vapor 46 of MTEOS is sprayed onto the surface of the resist film41 for 3 minutes, while the semiconductor substrate 40 is kept in theair at a temperature of 30° C. and a relative humidity of 95%, therebyselectively forming an oxide film 47 on the surface of the exposedportion 41a of the resist film 41. In this case, the acid resulting fromthe decomposition of NISS serves as a catalyst and induces a reaction asrepresented by the above Formula 2!, thereby forming the oxide film 47and generating an alcohol.

Next, as shown in FIG. 9(c), RIE is conducted using an O₂ plasma 48through the cured oxide film 47 serving as a mask, thereby forming aresist pattern 49. In this case, the RIE using an O₂ plasma is conductedby means of a parallel plate RIE apparatus under the conditions ofpower: 900 W, pressure: 0.7 Pa, and flow rate: 40 SCCM.

Thus, according to the fourth embodiment, the oxide film 47 isselectively formed on the surface of the resist film 41 and the RIEusing an O₂ plasma is performed with respect to the resist film 41through the oxide film 47 as a mask, thereby conducting dry development.As a result, the problem of pattern collapse due to wet development iseliminated, while the oxide film excellently retains its initialconfiguration. Consequently, a micropattern with a high aspect ratio canbe formed with high precision. Moreover, in the step of diffusing waterin the exposed portion 41a of the resist film 41, the depth reached bydiffused water can be controlled by regulating the period during whichthe water vapor 45 is supplied, i.e., the period during which thesemiconductor substrate 40 is kept in the air at a temperature of 30° C.and a relative humidity of 95%. Similarly to the first embodiment, wateris preferably diffused from the surface of the resist film 41 to a depthof 100 nm or more, since this prevents the oxide film 47 from flowing.

Although the fourth embodiment uses a copolymer of NISS and MMA as achemical amplification resist, it is also possible to use polyvinylphenol, a novolac resin, or the like as a compound which reacts with theacid, instead of MMA. As an acid generator, a generator of a sulfonicacid or the like may be used, instead of NISS. Although the fourthembodiment uses a resin containing 5-diazo-meldrum's acid as a contrastenhanced resin, another resin containing diazoketone or diazodiketonemay be used instead.

Although MTEOS is used as a metal alkoxide, it is also possible toalternatively use another metal alkoxide such astetramethylorthosilicate or tetraethylorthosilicate.

Although the RIE using an O₂ plasma is used as a method of drydevelopment, ECR using an O₂ plasma or the like may be used instead.

Although the KrF excimer laser light is used as a light source forexposure, it is also possible to alternatively use ArF excimer laserlight or an X-ray.

Although the semiconductor substrate 40 is kept in the water vapor inthe step of diffusing water in the surface of the exposed portion 41a ofthe resist film 41, it is also possible to alternatively supply water tothe resist film 41 overlying the semiconductor substrate 40.

(Fifth Embodiment)

FIGS. 10(a) to 10(c) to FIGS. 12(a) and 12(b) are cross sections showingindividual steps of a method of forming a micropattern according to afifth embodiment of the present invention. As a chemical amplificationresist, the fifth embodiment uses a copolymer of NISS and MMA.

Initially, as shown in FIG. 10(a), a resist composed of the abovechemical amplification resist is applied onto a semiconductor substrate50 made of silicon by spin coating and then heated for 60 seconds at atemperature of 90° C., thereby forming a resist film 51 with a thicknessof 1.2 μm. The resulting resist film 51 is then irradiated with KrFexcimer laser light 53 as an energy beam through a mask 52, therebytransferring the pattern of the mask 52 to the resist film 51 byexposure. As a result, NISS is decomposed in the surface of an exposedportion 51a of the resist film 51 to generate an acid, which renders thesurface of the exposed portion 51a of the resist film 51 hydrophilic.

Next, as shown in FIG. 10(b), the semiconductor substrate 50 is kept inair at a temperature of 30° C. and a relative humidity of 95% for aspecified period of time, thereby supplying water vapor 54 to thesurface of the resist film 51. As a result, the surface of the exposedarea 51a of the resist film 51 absorbs the water vapor 54, so that wateris diffused from the surface of the exposed portion 51a of the resistfilm 51 into a deep portion, e.g., a portion 100 nm deep.

Next, as shown in FIG. 10(c), vapor 55 of MTEOS is sprayed onto thesurface of the resist film 51 for, e.g., 30 seconds, while thesemiconductor substrate 50 is kept in the air at a temperature of 30° C.and a relative humidity of 95%. As a result, an oxide film 58 is formedon the surface of the exposed portion 51a of the resist film 51.

Next, as shown in FIG. 11(a), a dry nitrogen gas 57 is sprayed onto thesurface of the resist film 51 for, e.g., 30 seconds, thereby evaporatingthe alcohol contained in the oxide film 56. Thereafter, the spraying ofthe vapor 55 of MTEOS and the spraying of the nitrogen gas 57, eachdescribed above, are alternately performed about six times, therebychanging the entire exposed portion 51a of the resist film 51 into theoxide film 56. Thus, by alternately performing the processes ofsupplying the vapor 55 of MTEOS and drying with the nitrogen gas 57several times, the alcohol imparting mobility to the oxide film 56 iscompletely evaporated, so that the configuration of the oxide film 56 isremarkably improved.

Next, as shown in FIG. 12(b), RIE is conducted using an O₂ plasma 58through the oxide film 56 as a mask, thereby forming a resist pattern59. In this case, the RIE using the O₂ plasma is conducted by means of aparallel plate RIE apparatus under the conditions of power: 900 W,pressure: 0.7 Pa, and flow rate: 40 SCCM.

Although the fifth embodiment uses a copolymer of NISS and NMA as achemical amplification resist, it is also possible to use polyvinylphenol, a novolac resin, or the like as a compound which reacts with theacid, instead of MMA. As an acid generator, a generator of a sulfonicacid or the like may be used instead of NISS.

Although MTEOS is used as a metal alkoxide, it is also possible toalternatively use another metal alkoxide such astetramethylorthosilicate or tetraethylorthosilicate.

Although the RIE using the O₂ plasma is used as a method of drydevelopment, ECR using an O₂ plasma or the like may be used instead.

Although the KrF excimer laser light is used as a light source forexposure, ArF excimer laser light or an X-ray may be used instead.

Although the semiconductor substrate 50 is kept in the water vapor inthe step of diffusing water in the surface of the exposed portion 51a ofthe resist film 51, it is also possible to alternatively supply liquidwater to the resist film 51 overlying the semiconductor substrate 50.

(Sixth Embodiment)

FIGS. 13(a) to 13(c) and FIGS. 14(a) and 14(b) are cross sectionsshowing individual steps of a method of forming a micropattern accordingto a sixth embodiment of the present invention. As a chemicalamplification resist, the present embodiment uses a resist containing anacid generator which generates an acid in response to the radiation ofan energy beam and a compound which reacts with the acid, such as SAL601ER7 commercially available from Shipley Company.

Initially, as shown in FIG. 13(a), a resist film 61 composed of theabove chemical amplification resist is formed on a semiconductorsubstrate 60 made of silicon. The resulting resist film 61 is thenirradiated with KrF excimer laser light 63 as an energy beam through amask 62, thereby transferring the pattern of the mask 62 to the resistfilm 61 by exposure. As a result, an acid is generated in the surface ofan exposed portion 61a of the resist film 61.

Next, crosslinking is caused in the exposed portion 61a of the resistfilm 61 by applying heat at a temperature of 110° C. for 60 seconds,thereby forming a crosslinked portion 64, as shown in FIG. 13(b).

Subsequently, as shown in FIG. 13(c), a silylating solution 64 is kepton the surface of the resist film 61 for 1 minute to form a silylatedlayer 66 in an unexposed portion of the resist film 61, followed byrinsing with xylene. The silylating solution 65 is a mixture of 10 wt. %of hexamethylcyclotrisilazane, 2 wt. % of 1-methyl-2-pyrrolidone, and 88wt. % of xylene.

Next, as shown in FIG. 14(a), the silylated layer 66 is irradiated witha deep ultraviolet ray 67 as a high energy beam for 60 seconds, whileheating the semiconductor substrate 60 to 110° C., thereby increasingthe selectivity to the silylated layer 66 and the resist film 61. Sincethe silylated layer has not been irradiated with the high energy beam ina conventional embodiment, the reaction between silicon and the resistfilm does not proceed to a satisfactory degree, resulting in a lowselectivity to the silylated layer and the resist film. However, sincethe silylated layer 68 selectively formed is irradiated with the deepultraviolet ray 67 in the sixth embodiment, a carbon compound composingthe resist undergoes oxidative decomposition and volatilization,resulting in an increased concentration of silicon in the silylatedlayer 66 and a high selectivity to the silylated layer 66 and the resistfilm 61.

Next, as shown in FIG. 14(b), RIE is conducted using an O₂ plasma 68through the silylated layer 66 serving as a mask, thereby forming aresist pattern 69. In this case, the RIE using the O₂ plasma isconducted by means of a parallel plate RIE apparatus under theconditions of power: 900 W, pressure: 0.7 Pa, and flow rate: 40 SCCM.

                                      TABLE 2                                     __________________________________________________________________________            ETCHING RATE FOR                                                                         ETCHING RATE FOR                                           RADIATION OF                                                                          SILYLATED LAYER                                                                          UNSILYLATED                                                DEEP ULTRA-                                                                           (UNEXPOSED LAYER (EXPOSED                                                                           ETCHING                                         VIOLET RAY                                                                            PORTION ) (nm/min)                                                                       PORTION) (nm/min)                                                                        SELECTIVITY                                     __________________________________________________________________________    PRESENT 8.3        188.4      22.7                                            ABSENT  31.4       188.4      6.0                                             __________________________________________________________________________

Table 2! shows the etching rates for the silylated layer and unsilylatedlayer of the resist film and the etching selectivity to the silylatedlayer and unsilylated layer in the respective cases of the sixthembodiment and conventional embodiment. As shown in Table 2!, theetching selectivity in the case of not processing with the radiation ofthe deep ultraviolet ray (conventional embodiment) is 6, while theetching selectivity in the case of processing with the radiation of thedeep ultraviolet ray (sixth embodiment) is 22.7, which indicates thatthe etching selectivity has increased by three times or more. In thecase of not processing with the radiation of the deep ultraviolet ray,the obtained etching selectivity is low, so that there arise theproblems of deterioration of pattern configuration and difficulty informing a pattern with a high aspect ratio. In the sixth embodiment,however, the etching selectivity is increased by the irradiation of thesilylated layer 66 with the deep ultraviolet ray 65, so that a patternwith a high aspect ratio can be formed without suffering from patterncollapse and deterioration of its configuration.

Although the sixth embodiment uses SAL601 ER7 available from ShipleyCompany as a chemical amplification resist, it is also possible toalternatively use a resist having polyvinyl phenol, a novolac resin, orthe like as a compound which reacts with the acid.

Although the mixture of hexamethylcyclotrisilazane,1-methyl-2-pyrrolidone, and xylene is used as a silylating solution,another silylating agent, such as bis(dimethylamino)dimethylsilane, maybe used instead of hexamethylcyclotrisilazane andpropylene-glycol-methyl-ether-acetate may be used instead of1-methyl-2-pyrrolidone.

Although the RIE using the O₂ plasma is used as a method of drydevelopment, ECR (electron cyclotron resonance etching) using an O₂plasma or the like may be used instead.

Although the KrF excimer laser light is used as a light source forexposure, ArF excimer laser light or an X-ray may be used instead.

(Seventh Embodiment)

Below, a description will be given to a method of forming a micropatternaccording to a seventh embodiment of the present invention. The seventhembodiment uses a chemical amplification resist containing, as its maincomponents, an acid generator which generates an acid in response to theradiation of an energy beam and a polymer or monomer in which at lease apart of a phenolic hydroxy group is substituted by a protecting groupeliminated by the action of the acid. Initially, the above chemicalamplification resist is applied dropwise onto a semiconductor substrate,followed by spin coating for forming a resist film with a thickness of1.0 μm. The resulting resist film is then subjected to 1-minute bakingon a hot plate at 90° C.

Specific examples of the above polymer in which at least a part of aphenolic hydroxy group is substituted by a protecting group eliminatedby the action of the acid are poly(p-tert-butoxycarbonyloxystyrene),poly(p-tert-butoxystyrene), poly(p-tetrahydropyranyloxystyrene),poly(p-(1-ethoxyethoxy)styrene),poly(p-(1-methoxy-1-methylethoxy)styrene),poly(p-trimethylsilyloxystyrene),poly(p-tert-butoxycarbonyloxystyrene-p-hydroxystyrene),poly(p-tert-butoxystyrene-p-hydroxystyrene),poly(p-tetrahydfopyranyloxystyrene-p-hydroxystyrene),poly(p-(1-ethoxyethoxy)styrene-p-hydroxystyrene),poly(p-(1-methoxy-1-methylethoxy)styrene-p-hydroxystyrene),poly(p-trimethilsilyloxystyrene-p-hydroxystyrene),poly(p-tert-butoxycarbonylmethoxystyrene-p-hydroxystyrene), and thelike, but they are not limited thereto.

Specific examples of the above monomer in which at least a part of aphenolic hydroxy group is substituted by a protecting group eliminatedby the action of the acid are2,2-bis(4-tetrahydropyranyloxyphenyl)propane,2,2-bis(4-tert-butoxyphenyl)propane,2,2-bis(4-tert-butoxycarbonyloxyphenyl)propane,2,2-bis-4-(1-ethoxyethoxy)phenyl)propane,3,4-dihydro-4-(2,4-di-(1-tetrahydropyranyloxy)phenyl-7-(1-tetrahydropyranyloxy)-2,2,4-trimethyl-2H-1-benzopyran,3,4-dihydro-4-(2,4-di-(1-tert-butoxy)phenyl)-7-(1-tert-butoxy)-2,2,4-trimethyl-2H-1-benzopyran,3,4-dihydro-4-(2,4-di-(1-ethoxyethoxy)phenyl)-7-(1-ethoxyethoxy)-2,2,4-trimethyl-2H-1-1-benzopyran, and thelike, but they are not limited thereto.

The following are the compositions of materials of typical chemicalamplification resists.

    ______________________________________                                        (1st Example of Resist Materials)                                             poly(p-tert-butoxycarbonyloxystyrene-p-hydroxystyrene)                                                    6.0    g                                          (weight-average molecular weight of approximately 9500,                       monomer unit ratio of approximately 1:1)                                      triphenylsulfonium hexafluorophosphate                                                                    0.3    g                                          diethylene glycol dimethyl ether                                                                          13.7   g                                          (2nd Example of Resist Materials)                                             poly(p-(1-ethoxyethoxy)styrene-p-hydroxystyrene                                                           6.0    g                                          (weight-average molecular weight of approximately 10000,                      monomer unit ratio of approximately 1:1)                                      2-cyclohexylcarbonyl-2-(p-toluenesulfonyl)propane                                                         0.3    g                                          diethylene glycol dimethyl ether                                                                          13.7   g                                          (3rd Example of Resist Materials)                                             poly p-vinylphenol          5.0    g                                          (weight-average molecular weight of approximately 10000)                      2,2-bis(4-tetrahydropyranyloxyphenyl)propane                                                              1.5    g                                          2-cyclohexylcarbonyl-2-(p-toluenesulfonyl)propane                                                         0.3    g                                          diethylene glycol diethyl ether                                                                           13.2   g                                          (4th Example of Resist Materials)                                             poly(p-tert-butoxystyrene-p-hydroxystyrene)                                                               6.0    g                                          (weight-average molecular weight of approximately 10000,                      monomer unit ratio of approximately 1:1)                                      bis-cyclohexylsulfonyldiazomethane                                                                        0.3    g                                          diethylene glycol diethyl ether                                                                           13.7   g                                          (5th Example of Resist Materials)                                                                         5.0    g                                          poly p-vinylphenol (weight-average molecular weight of                        approximately 20000)                                                          3,4-dihydro-4-(2,4-di-(1-ethoxyethoxy)phenyl)-7-(1-ethoxy-                                                1.5    g                                          ethoxy)-2,2,4-trimethyl-2H-1-benzopyrane                                      2-cyclohexylcarbonyl-2-(p-toluenesulfonyl)propane                                                         0.3    g                                          3-methoxy-methyl propionate 13.2   g                                          (6th Example of Resist Materials)                                             poly(p-tetrahydropyranyloxystyrene-p-hydroxystyrene)                                                      6.0    g                                          (weight-average molecular weight of approximately 10000,                      monomer unit ratio of approximately 3:7)                                      2-cyclohexylcarbonyl-2-(p-toluenesulfonyl)propane                                                         0.3    g                                          2-heptanone                 13.7   g                                          (7th Example of Resist Materials)                                             poly(p-(1-methoxy-1-methylethoxy)styrene-p-hydroxystyrene)                                                6.0    g                                          (weight-average molecular weight of approximately 10000,                      monomer unit ratio of approximately 1:1)                                      p-toluenesulfonic acid 2,6-dinitrobenzyl                                                                  0.1    g                                          diethylene glycol dimethyl ether                                                                          13.9   g                                          (8th Example of Resist Materials)                                             m-cresol novolac resin      5.0    g                                          p-tetrahydropyranyloxystyrene                                                                             0.6    g                                          (weight-average molecular weight of approximately 10000)                      triphenylsulfonium hexafluorophosphate                                                                    0.1    g                                          diethylene glycol dimethyl ether                                                                          14.3   g                                          ______________________________________                                    

Next, the resist film is exposed to light of a wavelength of 248 nm froman excimer stepper having a numerical aperture of 0.42, followed by1-minute baking on a hot plate at a temperature of 100° C. The resistfilm is then subjected to 1-minute development with an organic alkalinesolution.

The seventh embodiment is characterized by the process of rinsing withpure water containing 0.1 wt. % of a surface-active agent such aspolyoxyethylene propylene glycol. As a result, even in a region having ahigh aspect ratio, a large surface tension is not exerted betweenadjacent resist patterns, so that the resist patterns are not leaningagainst their adjacent resist patterns. FIG. 15(a) shows a resistpattern 71A overlying a semiconductor substrate 70, which has beenformed by a conventional method similar to the seventh embodiment exceptfor a rinse, while FIG. 15(b) shows a resist pattern 71B overlying thesemiconductor substrate 70 formed by the seventh embodiment. As shown inFIG. 15(a), a part of the resist patterns formed by the conventionalmethod are leaning against their adjacent resist patterns. On theanother hand, the resist patterns formed by the seventh embodiment arenot leaning against any pattern, as shown in FIG. 15(b).

Instead of polyoxyethylene propylene glycol, ifpolyoxyethylene-p-nonylphenylether, polyoxyethylenecetylether,polyoxyethylenelaurylamineether, or polyoxyethylenelauryl ammoniumsulfate ether is used, the same effect can be obtained. Theconcentration of the surface-active agent is preferably 0.01 to 0.5 wt.%, though it is slightly different depending on the type of thesurface-active agent.

Although each of the above chemical amplification resists is positive,the method of forming a micropattern according to the seventh embodimentis also effective either in the case of using a negative chemicalamplification resist or in the case of using a normal positive ornegative resist.

We claim:
 1. A method of forming a micropattern comprising the stepsof:a first step of forming a resist film by applying, onto asemiconductor substrate, a resist containing a compound which iscrosslinked in response to the radiation of an energy beam; a secondstep of selectively exposing said resist film that was formed by saidfirst step by irradiating said resist film with a first energy beamthrough a mask so that an exposed portion of said resist film iscrosslinked; a third step of forming a silylated layer in an unexposedportion of said resist film irradiated with the first energy beam bysupplying a silylating agent to a surface of said resist film; a fourthstep of entirely irradiating said resist film including said silylatedlayer with a second energy beam so as to increase concentration ofsilicon in said silylated layer that was formed by said third step; anda fifth step of forming a resist pattern by performing etching withrespect to said resist film by using, as a mask, said silylated layerwhich has been irradiated with said second energy beam.